1. Field of the Invention
This invention relates to thermostats or controllers for heating systems such as solar heating systems wherein a fluid circulation pump is operated in response to the sensing of a differential temperature between a solar collector and a storage tank.
2. Description of the Prior Art
The prior art is generally cognizant of solar heating systems some of which are controlled in responsive to differential temperatures. U.S. Pat. No. 2,396,338 discloses a radiation heating and cooling system which includes a differential temperature responsive thermostat, constructed using fluid charged bulbs and bellows, to sense a temperature differential between a solar radiation portion and a tank to operate a valve controlling liquid circulation between the tank and solar radiation portion. U.S. Pat. No. 3,598,104 discloses a solar heating system for swimming pools using a surface temperature sensor and a subsurface temperature sensor connected in a bridge circuit with a comparator for operating a water circulation pump. U.S. Pats. No. 3,295,353 and 3,768,059 show other differential temperature responsive devices while U.S. Pats. Nos. 3,275,644 and 3,857,285 show electronic temperature responsive devices.